Ultrasonological characteristics of extraocular cysticercosis

Cysticercosis is a common ophthalmic parasitosis wherein humans are the intermediate hosts in the life cycle of the tape worm Taenia solium. While intraocular cysticercosis is more common and is more readily diagnosed clinically, recognition of extraocular cysticercosis needs supplementary imaging. Computed tomography (CT) and magnetic resonance imaging (MRI) have been extensively used to diagnose and characterize neurocysticercosis. Since the orbit is easily accessible to ultrasonography (USG), we evaluated its role in the diagnosis and management of extraocular cysticercosis. Serial A- and B- scan ultrasonograms from 24 patients with extraocular cysticercosis were analyzed to determine features at various stages of evolution of the lesion and an attempt was made to classify the lesion on this basis. Of 24 patients, 23 had a cyst clearly demonstrable by USG: 22 within or attached to an extraocular muscle (with or without myositis) and one free in the orbit. One patient had an optic nerve cyst not detected by USG but by CT scan. Cysts at various stages of evolution were found - viable, degenerating and inactive. The therapeutic response of the cyst to treatment with oral albendazole could be effectively studied and monitored by sequential USG. Orbital ultrasound is a practical, precise and cost-effective imaging modality to diagnose, manage and monitor extraocular cysticercosis, although it can not completely replace CT and MRI.